Multiple function current-sharing charging system and method

ABSTRACT

Multiple function current-sharing charging systems and methods are provided. Where first and second rechargeable power supplies are connected to a charging system, a first charging current is provided to the first rechargeable power supply and a second charging current is provided to the second rechargeable power supply. Upon detection of a predetermined charge level of one of the rechargeable power supplies, a third charging current is provided to the first rechargeable power supply and a fourth charging current is provided to the second rechargeable power supply.

CROSS-REFERENCE TO RELATED APPLICATIONS

This continuation application claims priority to U.S. patent applicationSer. No. 10/834,283, filed Apr. 29, 2004, by Ryan M. Bayne, et al,entitled “Multiple Function Current-Sharing Charging System and Method”(10933-US-PAT-4214-00500), and which is incorporated by reference hereinas if reproduced in its entirety.

BACKGROUND

This invention relates generally to charging of rechargeable powersupplies such as batteries.

Providing an external source of power to a portable device, such as apersonal digital assistant (“PDA”), a mobile communication device, acellular phone, a wireless two-way e-mail communication device, andother types of device, requires design considerations with respect toboth the device and the power source. For example, many portable devicesprovide a power interface for receiving power from a power source, forinstance to recharge a battery installed in the device. Charging systemsconfigured for charging rechargeable batteries or other rechargeablepower supplies that have been removed from a device are also known.Another known type of charging system is a multiple function chargingsystem configured to charge a power supply whether it is installed in adevice or removed from the device.

Multiple function charging systems enabled for connection of more thanone power supply at a time generally charge power supplies in a serialfashion. One power supply is typically charged at a time. Although morethan one power supply, such as a device with a battery installed and aspare battery, may be connected to the charging system, charging currentis applied to only one power supply at any time. As such, known multiplefunction chargers offer no charging time advantage over charging systemsthat accept only one power supply at a time. In the above example of adevice and a spare battery simultaneously connected to a chargingsystem, the battery inside the device is normally charged first, andonly then is the spare battery charged. The total charging time for thedevice battery and the spare battery is substantially the same as thetime required to charge each battery separately.

SUMMARY

According to an aspect of the invention, a multiple functioncurrent-sharing charging system comprises a power source interfaceconfigured to receive energy from a power source, a power converterconnected to the power source and configured to regulate the energyreceived from the power source and to output charging current, aplurality of power supply interfaces configured for connection torespective rechargeable power supplies, and a charging controllerconnected to the power converter to receive the charging current and tothe plurality of power supply interfaces, and configured to detectconnection of a first rechargeable power supply to a first one of theplurality of power supply interfaces, to determine whether a secondrechargeable power supply is connected to a second of the plurality ofpower supply interfaces, and to provide a first charging current to oneof the first and second rechargeable power supplies and a secondcharging current to the other of the first and second rechargeable powersupplies where a second rechargeable power supply is connected to asecond of the plurality of power supply interfaces.

In accordance with another aspect of the invention, a current-sharingcharging method for a multiple function charging system comprises thesteps of detecting connection of a first rechargeable power supply tothe charging system, determining whether a second rechargeable powersupply is connected to the charging system, and where a secondrechargeable power supply is connected to the charging system, providinga first charging current to the first rechargeable power supply, andproviding a second charging current to the second rechargeable powersupply.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention identified in the claims may be more clearlyunderstood, preferred embodiments thereof will be described in detail byway of example, with reference to the accompanying drawings, in which;

FIG. 1 is a block diagram of a multiple function current-sharingcharging system.

FIG. 2 is a block diagram of a multiple function charging systemconnected to a mobile device and a battery.

FIG. 3 is a block diagram of a multiple function current-sharingcharging system incorporating a Universal Serial Bus (USB) interface anda battery receptacle.

FIG. 4 is a flow diagram illustrating a current-sharing charging method.

FIG. 5 is a block diagram of a wireless mobile communication device.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a multiple function current-sharingcharging system. The charging system 10 includes a power sourceinterface 12, a power converter 14, a charging controller 16, andrechargeable power supply interfaces 17 and 18.

The power source interface 12 is configured for connection to a powersource from which rechargeable power supplies are charged. In oneembodiment, the power source interface 12 is a plug unit that can beused to couple with a conventional power socket to receive powertherefrom. For example, such a plug unit may be a two prong or threeprong plug of the type used in North America that can couple to a NorthAmerican AC power socket. Alternatively, the power source interface 12can accept one or more types of plug adapters configured to couple thepower source interface 12 to corresponding types of power sockets. Theuse of interchangeable plug adapters has the advantage of allowing thesame charging system to be used with a variety of types of powersources, depending on availability. Thus, the power source interface 12is configured to receive energy from a power source either directly orthrough the use of a plug adapter, and is operative to transfer thereceived energy to the power converter 14.

A power converter such as 14 typically includes at least one of thefollowing components: a switching converter, a transformer, a DC source,a voltage regulator, linear regulator, and a rectifier. The powerconverter 14 is operative to receive energy from a power source throughthe power source interface 12, and to convert that received energy to aform that can be used to charge power supplies connected to the chargingsystem 10. For example, the power converter 14 can be of substantiallyconventional construction, such as a switching power converter thatconverts 115 VAC to 5 VDC. DC-to-DC converters or DC regulators, whichconvert DC inputs to DC outputs are also common in such powerconverters. In one embodiment, the power converter 14 is adapted toaccept a wide range of input energy levels and frequencies from thepower source interface 12. Alternatively, the power converter 14 isadapted to accept a limited range of input energy levels andfrequencies, and the power source interface 12, or each plug adapter ifany, is operable to convert the input energy levels and frequencies intoa range that the power converter 14 can accommodate. The power converter14 provides its energy output to the charging controller 16.

The charging controller 16 controls the amount of charging currentapplied to each rechargeable power supply connected to the power supplyinterfaces 17 and 18. Where only one power supply is connected to aninterface 17 or 18, the charging controller 16 outputs full chargingcurrent, which may vary between different power supplies or types ofpower supply, to that power supply. The charging controller 16 is alsoconfigured to implement current sharing between multiple connected powersupplies, as described in further detail below. Although the chargingcontroller 16 is preferably implemented in firmware, such as amicroprocessor executing charging control software, those skilled in theart appreciate that hardware implementations of the charging controller16 are also possible.

Each power supply interface 17 and 18 is compatible with a charginginput on a corresponding power supply. The power supply interfaces 17and 18 may be of the same or different types. For example, in onepossible embodiment, the power supply interface 17 is configured fordirect connection to a battery, whereas the power supply interface 18 isconfigured for connection to battery through other circuits orcomponents in a device in which a battery is installed. Alternatively, apower supply interface 17 or 18, or each of the interfaces, isconfigured to receive power supply adapters so as to indirectly connectto different types of power supplies.

In operation, the charging controller 16 detects the connection of arechargeable power supply to a power supply interface 17 or 18. If eachpower supply interface 17 and 18 is configured for connection to aparticular type of power supply, then the charging controller determinesthe type of a power supply, and thus the appropriate charging currentsfor the power supply, by determining to which power supply interface 17or 18 the power supply is connected. Otherwise, the charging controllerdetects the type of connected power supply, for example, by performingvoltage and current tests on the power supply.

If only one power supply is connected to a power supply interface 17 or18, then a full charging current is output to that power supply by thecharging system 10. As described briefly above and in more detail belowin the context of a battery and a device, full charging currents may bedifferent for different types of device. In accordance with an aspect ofthe invention, where a power supply is connected to each power supplyinterface 17 and 18, the charging controller shares available chargingcurrent between each power supply. Since the charging system 10 istypically capable of supplying more charging current than one powersupply draws, full charging current is supplied to one of the connectedpower supplies, and any or all available excess charging current isoutput to the other connected power supply by the charging controller16. Thus, one power supply receives full charging current, and the otherreceives remaining available charging current, referred to hereinprimarily as “trickle” charging current.

Those skilled in the art will appreciate that an amount of tricklecharging current available is dependent upon such factors as the outputcharacteristics of the charging system 10 and the full charging currentof the connected power supplies. In alternate embodiments, the chargingcontroller 16 is configured to output a predetermined trickle chargingcurrent or a variable trickle charging current dependent upon theavailable excess charging current.

The charging controller 16 also detects a charge level of each connectedpower supply. Initially, the power supply that receives its fullcharging current charges faster than the other power supply. When thefull charging power supply is charged to a predetermined level, which isdetected by the charging controller 16 by monitoring charging current orterminal voltage of that power supply, for example, the chargingcontroller 16 switches full charging current to the other power supply,and trickle charging current to the power supply that was previouslyreceiving full charging current. The charging controller 16 comparesvoltage and/or current levels to respective thresholds, which may bedifferent for different power supplies, to determine when to switchbetween full charging current and trickle charging current. In afirmware implementation, a microprocessor in the charging controller 16receives voltage and/or current level indications on input pinsconnected to voltage and current sensing circuits and software executedby the microprocessor performs the comparison and initiates the switchbetween full and trickle charging currents.

In conventional multiple function charging systems, power supplies arecharged serially, such that one connected power supply receives its fullcharging current while the other receives no charging current. When onepower supply is fully charged, its charging current is turned off, andthe other power supply receives its full charging current. Totalcharging time for two power supplies is therefore equal to the separatecharging time for each power supply. Current sharing as described hereinprovides both full charging current to one power supply and tricklecharging current to another power supply. As such, the other powersupply is slowly charging even while the one power supply is receivingits full charging current. When the charging controller 16 switches fullcharging current to the other power supply, it has already partiallycharged, which thereby reduces the total charging time for the two powersupplies relative to conventional charging systems.

Although reference is made to full charging current and trickle chargingcurrent in the foregoing description, it should be appreciated that theinvention is in no way restricted to any particular charging currentlevels. Where multiple power supplies are connected to a chargingsystem, the charging controller 16 provides a first charging current toa first power supply and a second charging current to a second powersupply. When the first power supply has charged to a predeterminedlevel, a third charging current lower than the first charging current isoutput to the first power supply and a fourth charging current higherthan the second charging current is output to the second power supply.In the preceding description, the first and fourth charging currents arethe full charging currents of each power supply, and the second andthird charging currents correspond to the trickle charging current.

FIG. 2 is a block diagram of a multiple function charging systemconnected to a mobile device and a battery. In the charging system 20,the components 22, 24, 26, 27, and 28 are substantially the same as thesimilarly-labelled components in FIG. 1, except that the rechargeablepower supply interfaces 27 and 28 are a battery interface and a deviceinterface, respectively. In the embodiment shown in FIG. 2, the chargingsystem 20 is configured for use with both a battery 30 and a device 32.

The battery interface 27, or an adapter configured for connection to thebattery interface 27, is compatible with connectors in the battery 30.Where the battery 30 is a spare battery for the device 32, for example,the battery interface 27 may be similar to an interface (not shown)associated with in the power distribution and charging subsystem 36.Similarly, the device interface 28 is compatible with the deviceinterface 34 or an interchangeable adapter compatible with bothinterfaces 28 and 34.

The device 32 may be a wireless mobile communication device such as adual-mode data and voice communication device, a mobile telephone withor without data communications functionality, or a data communicationdevice, for example, or another portable device, with or withoutcommunications capabilities. Even though wireless communication devicesare one of the most common types of devices with which charging systemsare used, the present invention is in no way restricted to communicationdevices, or any other type of device. Current-sharing charging asdescribed herein is applicable to other types of devices andrechargeable power supplies.

The battery 38 supplies power for the device 32 through the powerdistribution and charging subsystem 36. The power distribution andcharging subsystem 36 preferably uses the power provided by the chargingsystem 20 to provide operating power to the device 32 and to charge thebattery 38. The particular design of the power distribution and chargingsubsystem 36 is dependent upon the type of the device 32, as will beapparent to those skilled in the art, and is substantially independentof the current-sharing scheme implemented in the charging system 20.

If only the battery 30 or the device 32 is connected to the chargingsystem 20, then the charging controller 26 determines which one of thebattery 30 and the device 32 is connected, and outputs the correspondingfull charging current to the appropriate interface 27 or 28. Althoughthe battery 30 and the battery 38 may be the same type of battery, thefull charging currents may different, since the battery 38 is installedin the device 32. As described above, the power distribution andcharging subsystem 36 preferably uses power received from the chargingsystem 20 to both power the device 32 and charge the battery 38. Assuch, the device 32 may draw higher current from the charging system 20due to the additional power requirements of other components in thedevice 32 to which power is distributed by the power distribution andcharging subsystem 36. For example, the battery 30 may be rated for atypical full charging current of 700 mA, whereas the device 32 is ratedfor a typical full charging current of 750 mA.

When both the battery 30 and the device 32 are connected to the chargingsubsystem 20, the charging controller 26 distributes full chargingcurrent to one, and trickle charging current to the other. In mostcases, a user would prefer to charge the device 32 first so that thedevice can be disconnected from the charging system 20. However, thecharging controller 26 may alternatively be configured to designate thebattery 30 as a primary power supply for initial full charging currentand the device 32 as a secondary power supply for initial tricklecharging. Manual selection of the primary power supply, using a switchon the charging system 20, for example, or a configurable system inwhich a device provides to the charging system 20 an indication of itsrank or precedence, are also contemplated.

In order to further illustrate current-sharing charging, consider anillustrative example in which the charging system 20 has a maximumoutput of 825 mA, the battery 30 is the secondary power supply and has afull charging current of 700 mA, and the device 32 is the primary powersupply and has a full charging current of 750 mA. The chargingcontroller 26 detects the connection of both rechargeable power supplies(i.e., the battery 30 and the device 32) to the interfaces 27 and 28,and supplies the full charging current of 750 mA to the device 32. Thecharging controller 26 also provides trickle charging current to thebattery 30. As described above, trickle charging current may be set at apredetermined level at or below the available excess charging current,which is 825 mA maximum output of the charging system 20 less the 750 mAdrawn by the device 32, or 75 mA. For the purposes of this example,trickle charging current is set at 50 mA. Therefore, initially, thedevice 32 draws its full charging current of 750 mA, and the battery 30draws trickle charging current of 50 mA.

After the battery 38 in the device 32 has been charged to apredetermined level, as determined based on a measured terminal voltage,for example, the charging controller 26 provides the battery 30 with itsfull charging current of 700 mA and switches the device 32 to thetrickle charging current of 50 mA. When both the battery 30 and thebattery 38 are fully charged, the charging system 20 preferably entersan idle state and no further charging current is drawn from the chargingsystem 20. In some implementations, the charging controller 26 may beconfigured to continue to provide operating power to the device 32 sothat battery power is conserved until the device 32 is disconnected fromthe charging system 20.

Other switching schemes and current sharing schemes will also be obviousto those skilled in the art, and as such, are considered to be withinthe scope of the invention. For example, many known charging systemsprovide several charging phases. A constant current charging phaseduring which a constant full charging current is provided to a powersupply until the power supply reaches a predetermined terminal voltageis common. After the power supply reaches the predetermined terminalvoltage, a constant voltage charging phase provides decreasing levels ofcharging current to the power supply to maintain the terminal voltage.When the power supply draws less than a predetermined amount of current,a typically time-limited top-off charging phase completes the chargingcycle. In the example above, full to trickle charging current switchingis based on terminal voltage of a primary power supply, and thus maycoincide with a transition from a constant current charging phase to aconstant voltage charging phase. Alternatively, the full to tricklecharging current switching may be dependent upon the charging currentdrawn by the primary power supply, coinciding with the constant voltagecharging phase to top-off charging phase transition, for example. Wheretrickle charging current is not set to a predetermined current as above,the charging controller 26 could be configured for “gradual” switchingbetween full and trickle charging current. In the above example, ascharging current drawn by the device 32 decreases during a constantvoltage charging phase, more charging current could be supplied to thebattery 30. After the device 32 draws less than 825−700=125 mA, thebattery 30 receives its full charging current of 700 mA from thecharging system 20.

FIG. 3 is a block diagram of a multiple function current-sharingcharging system incorporating a USB interface and a battery receptacle.In FIG. 3, dashed lines indicate power transfer, while solid lines areused for data connections. The charging system 40 is substantially thesame as the charging systems 10 and 20, except that the power supplyinterfaces are a battery receptacle 47 and a USB interface 48.

The battery receptacle 47 is configured to receive the battery 52, whichis a spare battery for the device 54 in one embodiment. In this case,the battery receptacle 47 is substantially similar to the batteryreceptacle 60, although the battery receptacle 47 need not necessarilytransfer power from the battery 52 to the charging system 40.

The device 54 is also substantially similar to the device 32, includinga USB interface 56 to the charging system 40, a power distribution andcharging subsystem 58, and a battery 62. Although an interface to thebattery 38 is inherent in the power distribution and charging subsystem36 in FIG. 2, the battery receptacle 60 is an example of such aninterface. The device 54 also includes a USB port 64 and amicroprocessor 66. In the device 54, the power distribution and chargingsubsystem 58 provides operating power to the microprocessor 66 and otherdevice components. A data connection between the microprocessor 66 andthe power distribution and charging subsystem 58 provides forsoftware-based control and monitoring of the power distribution andcharging subsystem 58, so that the microprocessor 66 can determine aremaining charge level of the battery 62 and provide an indication ofbattery charge to a user, for example.

Typically, USB devices can draw limited current from a USB host. In thecase of a charging system, such a limit may be undesirable. Therefore,when the device 54 is connected to the USB interface 48, anidentification signal is preferably provided to the device 54 to notifythe device 54 that it is connected to a power source that is not subjectto the normal power limits imposed by the USB specification. Such anidentification signal is provided, for example, by the chargingcontroller 46. The device 54, or in most implementations themicroprocessor 66, recognizes the identification signal and enables thepower distribution and charging system to draw power through Vbus andGnd lines of the USB interface 56 without waiting for the normal USBprocesses of enumeration or charge negotiation.

The detection of the identification signal may be accomplished using avariety of methods. For example, the microprocessor 66 may detect theidentification signal by detecting the presence of an abnormal data linecondition at the USB port 64. The detection may also be accomplishedthrough the use of other device subsystems in the device 54. Onepreferred identification signal results from the application of voltagesignals greater than 2 volts to both the D+ and D− lines in the USBinterface 48 by the charging controller 46, which can then be detectedat the device 54. Further details of USB-based charging are provided inthe following U.S. patent applications: Ser. Nos. 10/087,629, and10/087,391, both filed on Mar. 1, 2002 and assigned to the owner of theinstant application. The disclosure of each of these applications,including the specification and drawings thereof, is hereby incorporatedin its entirety herein by reference.

Operation of the charging system 40 is substantially as described above.Either the battery 52 or the device 54 is provided with its fullcharging current, while the other receives trickle charging current.When full charging device is charged to a predetermined level, then thecharging controller switches the trickle charging device to fullcharging current and vice-versa. However, the USB connection between thedevice 54 and the charging system 40 could be further exploited beyondcharging the device 54. For example, charging level determination forthe battery 62 could be left to the device 54 instead of the chargingcontroller 46. A data connection (not shown) between the USB interfaces56 and 48 allows the device microprocessor 66 to signal the chargingcontroller 46 when the battery 62 reaches a predetermined charginglevel. As shown, the USB interface 56 may also be connected to other USBinterfaces in other devices or systems, to support such extendedfunctions as indirectly charging such other devices and systems throughthe device 54 through a conventional USB connection. The device 54 thenprovides an interface to a power supply that is not itself compatiblewith the charging system 40.

FIG. 4 is a flow diagram illustrating a current-sharing charging method.The steps in the method have been described in detail above and aretherefore described briefly below.

The method begins at step 72, in which connection of a rechargeablepower supply to an interface is detected. At step 74, a determination ismade as to whether another power supply is connected. If so, then fullcharging current is provided to one power supply, the primary powersupply, and trickle charging current is provided to the other,secondary, power supply. Step 78 illustrates monitoring of the charginglevel of the primary power supply. When the primary power supply ischarged to a predetermined level, the secondary power supply is switchedto full charging current and the primary power supply is switched totrickle charging current. When the secondary power supply is charged, asdetermined at step 82, charging is complete, as indicated at 84.

Where no other power supply is connected, as determined at step 74, theconnected power supply is provided with its full charging current atstep 86. If it is determined at step 88 that another power supply issubsequently connected to the charging system, then the method revertsto step 76. Otherwise, the power supply receives its full chargingcurrent until it is determined at step 90 that the power supply ischarged.

The method shown in FIG. 4 and described above is one illustrativeexample of a current-sharing charging method. Modifications of themethod are possible without departing from the invention. For example,the current-sharing method in FIG. 4 could be adapted to amultiple-phase charging cycle including a constant current phase, aconstant voltage phase, and a time-limited top-off charging phase, asdescribed above. In addition, just as the method reverts to step 76 fromstep 88 when a second power supply is connected, the method proceeds tostep 86 if the primary power supply is disconnected while the secondarypower supply is receiving trickle charge. Further, although the decisionsteps 78, 82, 88 and 90 are shown as separate steps, it should beappreciated that these steps may instead be monitoring operations thatare performed during power supply charging. For instance, the chargingat steps 76, 80, and 86 need not be halted to check a power supplycharge level at steps 78, 82, and 90. Charge level is preferablymonitored during charging. Similarly, detection of another power supplyat step 88 preferably interrupts the charging at step 86, but theoperation of detecting whether another power supply has been connected,such as by polling an interface or monitoring for a detection signal,preferably does not require the charging to be halted.

FIG. 5 is a block diagram of a wireless mobile communication device,which is one type of device for which the current-sharing chargingschemes disclosed herein is applicable. The wireless mobilecommunication device (“mobile device”) 100 is preferably a two-waycommunication device having at least voice or data communicationcapabilities. Preferably, the mobile device 100 is also capable ofcommunicating over the Internet, for example, via a radio frequency(“RF”) link.

The exemplary mobile device 100 comprises a microprocessor 112, acommunication subsystem 114, input/output (“I/O”) devices 116, a USBport 118, and a power subsystem 120. The microprocessor 112 controls theoverall operation of the mobile device 100. The communication subsystem114 provides the mobile device 100 with the ability to communicatewirelessly with external devices such as other mobile devices and othercomputers. The I/O devices 116 provide the mobile device 100 withinput/output capabilities for use with a device user. The USB port 118provides the mobile device 100 with a serial port for linking directlywith other computers and/or a means for receiving power from an externalpower source, as described above. The power subsystem 120 provides themobile device 100 with a local power source.

The communication subsystem 114 comprises a receiver 122, a transmitter124, antenna elements 126 and 128, local oscillators (LOs) 130, and adigital signal processor (DSP) 132. The particular design of thecommunication subsystem 114 and the components used therein can vary. Itwould be apparent to one of ordinary skill in the art to design anappropriate communication subsystem using conventional methods andcomponents to operate over a communication network 134 based on theparameters necessary to operate over that communication network. Forexample, a mobile device 100 geographically located in North America mayinclude a communication subsystem 114 designed to operate within theMobitex™ mobile communication system or DataTAC™ mobile communicationsystem, whereas a mobile device 100 intended for use in Europe mayincorporate a General Packet Radio Service (GPRS) communicationsubsystem 114.

Network access requirements will also vary depending upon the type ofnetwork 134. For example, in the Mobitex and DataTAC networks, mobiledevices 100 are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks however, network access is associated with a subscriber or userof a mobile device 100. A GPRS device therefore requires a subscriberidentity module (not shown), commonly referred to as a SIM card, inorder to operate on a GPRS network. Without a SIM card, a GPRS devicewill not be fully functional. Local or non-network communicationfunctions (if any) may be operable, but the mobile device 100 will beunable to carry out any functions involving communications over thenetwork 134, other than legally required functions such as ‘911’emergency calling.

When required, after the network registration or activation procedureshave been completed, a mobile device 100 may send and receivecommunication signals over the network 134. Signals received by theantenna element 126 are input to the receiver 122, which typicallyperforms such common receiver functions as signal amplification,frequency down conversion, filtering, channel selection, and in theexemplary system shown in FIG. 5, analog to digital conversion. Analogto digital conversion of a received signal allows more complexcommunication functions such as demodulation and decoding to beperformed in the DSP 132. Similarly, signals to be transmitted areprocessed, including modulation and encoding for example, by the DSP 132and input to the transmitter 124 for digital to analog conversion,frequency up conversion, filtering, amplification, and transmission overthe communication network 134 via the transmitter antenna element 128.The DSP 132 not only processes communication signals, but also providesfor receiver and transmitter control. For example, signal gains appliedto communication signals in the receiver 122 and transmitter 124 may beadaptively controlled through automatic gain control algorithmsimplemented in the DSP 132.

In implementing its device operation control function, themicroprocessor 112 executes an operating system. The operating systemsoftware used by the microprocessor 112 is preferably stored in apersistent store such as the non-volatile memory 136, or alternativelyread only memory (ROM) or similar storage element. The microprocessor112 may also enable the execution of specific device softwareapplications, which preferably are also stored in a persistent store.The operating system, specific device applications, or parts thereof,may also be temporarily loaded into a volatile store such as in RAM 138.The non-volatile memory 136 may be implemented, for example, as a flashmemory component, or a battery backed-up RAM, for example.

A predetermined set of software applications which control basic deviceoperations, including at least data and voice communication applicationsfor example, will normally be installed on the mobile device 100 duringmanufacture. One such application loaded on the mobile device 100 couldbe a personal information manager (PIM) application. The PIM applicationis preferably a software application for organizing and managing userinputted data items such as e-mail, calendar events, voice mails,appointments, and task items. The PIM data items may be stored in theRAM 138 and/or the non-volatile memory 136.

The PIM application preferably has the ability to send and receive dataitems, via the wireless network 134. The PIM data items are preferablyseamlessly integrated, synchronized and updated, via the wirelessnetwork 134, with corresponding data items stored or associated with ahost computer system (not shown) used by the device user. Thesynchronization of PIM data items is a process by which the PIM dataitems on the mobile device 100 and the PIM data items on the hostcomputer system can be made to mirror each other.

There are several possible mechanisms for loading software applicationsonto the mobile device 100. For example, software applications may beloaded onto the mobile device 100 through the wireless network 134, anauxiliary I/O subsystem 140, the USB port 118, a short-rangecommunications subsystem 142, such as an infrared (“IR”), Bluetooth™, or802.11 communication system, or any other suitable subsystem 44. Thoseskilled in the art will appreciated that “Bluetooth” and “802.11” referto sets of specifications, available from the Institute for Electricaland Electronics Engineers (IEEE), relating to wireless personal areanetworks and wireless local area networks, respectively.

When loading software applications onto the mobile device 100, thedevice user may install the applications in the RAM 138 or thenon-volatile memory 136 for execution by the microprocessor 112. Theavailable application installation mechanisms can increase the utilityof the mobile device 100 by providing the device user with a way ofupgrading the mobile device 100 with additional and/or enhancedon-device functions, communication-related functions, or both. Forexample, a secure communication application may be loaded onto themobile device 100 that allows for electronic commerce functions or otherfinancial transactions to be performed using the mobile device 100.

The I/O devices 116 are used to accept inputs from and provide outputsto a user of the mobile device 100. In one mode of operation, a signalreceived by the mobile device 100, such as a text message or web pagedownload, is received and processed by the communication subsystem 114,forwarded to the microprocessor 112, which will preferably furtherprocess the received signal and provides the processed signal to one ormore of the I/O devices 116 such as the display 146. Alternatively, areceived signal such as a voice signal is provided to the speaker 148,or alternatively to an auxiliary I/O device 140. In another mode ofoperation, a device user composes a data item such as an e-mail messageusing a keyboard 150 in cooperation with the display 146 and/or possiblyan auxiliary I/O device 140. The composed data item may then betransmitted over a communication network 134 using the communicationsubsystem 114. Alternatively, a device user may compose a voice messagevia a microphone 152, or participate in a telephone call using themicrophone 152 and the speaker 148.

The short-range communications subsystem 142 allows the mobile device100 to communicate with other systems or devices, which need notnecessarily be similar to device 100. For example, the short-rangecommunications subsystem 142 may include an infrared device, a Bluetoothmodule, or an 802.11 module, as described above, to supportcommunications with similarly-enabled systems and devices.

The USB port 118 provides the mobile device 10 with a serial port forlinking directly with other computers to exchange data and/or to receivepower. The USB port 118 also provides the mobile device 100 with a meansfor receiving power from an external power source. For example, in apersonal digital assistant (PDA)-type communication device, the USB port118 could be used to allow the mobile device 100 to synchronize datawith a user's desktop computer (not shown). The USB port 118 could alsoenable a user to set parameters in the mobile device 100 such aspreferences through the use of an external device or softwareapplication. In addition, the USB port 118 provides a means fordownloading information or software to the mobile device 100 withoutusing the wireless communication network 134. The USB port 118 providesa direct and thus reliable and trusted connection that may, for example,be used to load an encryption key onto the mobile device 100 therebyenabling secure device communication.

Coupled to the USB port 118 is a USB interface 154. The USB interface154 is the physical component that couples the USB port to the outsideworld. In the exemplary mobile device 100, the USB interface 154 is usedto transmit and receive data from an external data/power source 156,receive power from the external data/power source 156, direct thetransmitted/received data from/to the USB port 118, and direct thereceived power to the power subsystem 120.

The power subsystem 120 comprises a charging and power distributionsubsystem 158 and a battery 160, which have been described above. Inconjunction with a charging system connected as the data/power source156, current-sharing charging of the mobile device 100 and a sparebattery therefor, in accordance with aspects of the present invention,is supported.

This written description may enable those skilled in the art to make anduse embodiments having alternative elements that correspond to theelements of the invention recited in the claims. The intended scope ofthe invention thus includes other structures, systems or methods that donot differ from the literal language of the claims, and further includesother structures, systems or methods with insubstantial differences fromthe literal language of the claims.

For example, it would be obvious to implement current-sharing chargingfor more than two power supplies. In this case, a primary power supplyreceives its full charging current, and available excess chargingcurrent is then distributed among one or more secondary power supplies.

1. A method of charging two rechargeable power supplies comprising:providing a charging system; providing a universal serial bus (USB)connection; sending an identification signal via the USB connection,using the USB's data lines; providing a first charging current to afirst rechargeable power supply via the USB connection using the V-buspower line, the first charging current enabled to exceed USB currentdraw limitations; recognizing the identification signal to draw thefirst charging current at a level that exceeds USB current drawlimitations; drawing the first charging current that exceeds USB currentdraw limitations; determining an available second charging current basedon a difference between the first charging current and a maximum outputof the charging system; and while continuing to provide the firstcharging current using the USB's V-bus power line, charging a secondrechargeable power supply by providing the second charging current basedon the available second charging current.
 2. The method of claim 1 wherethe second charging current comprises the majority of the availablesecond charging current.
 3. The method of claim 1 further comprising:determining that the first rechargeable power supply is substantiallycharged; and applying to the second charging current a full chargingcurrent of the second rechargeable power supply.
 4. The method of claim1 where the second rechargeable power supply comprises a rechargeablebattery configured to be substitutable for a battery in the firstrechargeable power supply.
 5. The method of claim 1 where as the firstrechargeable power supply charges, gradually reducing power of the firstcharging current applied to the first rechargeable power supply.
 6. Amethod of charging two rechargeable power supplies, the power suppliesin devices, comprising: providing a charging system; providing universalserial bus (USB) connections at the charging system and the devices;sending an identification signal via a first USB connection, using thefirst USB's data lines, to a first device with a first rechargeablepower supply; sending an identification signal via a second USBconnection, using the second USB's data lines, to a second device with asecond rechargeable power supply; providing a first charging current tothe first rechargeable power supply via the first USB connection using afirst V-bus power line, the first charging current enabled to exceed USBcurrent draw limitations; recognizing the identification signal to drawthe first charging current at a level that exceeds USB current drawlimitations; drawing the first charging current such that USB currentdraw limitations are exceeded; determining an available second chargingcurrent based on a difference between the first charging current and amaximum output of the charging system; and while continuing to providethe first charging current using the USB's V-bus power line, charging asecond rechargeable power supply by providing a second charging currentbased on the available second charging current.
 7. The method of claim 6further comprising: recognizing the identification signal to draw thesecond charging current at a level that exceeds USB current drawlimitations; and drawing the second charging current such that USBcurrent draw limitations are exceeded.
 8. The method of claim 7 wherethe second charging current comprises the majority of the availablesecond charging current.
 9. The method of claim 6 further comprising:determining that the first rechargeable power supply is substantiallycharged; and applying to the second charging current a full chargingcurrent of the second rechargeable power supply.